A wide variety of spray equipment for applying liquids such as paint, varnish, cleaning solvents, or other liquid materials to a surface are known. Typically, such spray equipment includes a spray gun having a needle assembly, a flow nozzle, and an air cap that are selected as an operating set based on the viscosity of the liquid that is being sprayed. For example, when painting an automobile, a first operating set of needle assembly, flow nozzle, and air cap may be used for applying a base coat, a second operating set of these components may be used for applying a top coat, and a third operating set of these components may be used for applying a clear coat.
Prior art spray apparatus are generally characterized as having many individual parts that are assembled together in a complex, highly interdependent manner into a single housing. Using a prior art spray apparatus, when an operator decides to change one of the or more of the parts, such as the needle assembly, the operator must laboriously disassemble numerous other parts of the spray apparatus to get to the needle assembly. Thus, in the above-referenced example of painting an automobile, when the operator desires to switching from a first operating set (i.e. needle assembly, nozzle, and air cap) to a second operating set, the spray apparatus must be meticulously disassembled, and each individual component (needle assembly, flow nozzle, and air cap) individually replaced. Then, prior to using the spray equipment, all of the replacement components of the second operating set must be reinstalled into the housing. This process takes considerable time and effort each time the operator desires to switch from one operating set to another, thereby decreasing operational efficiency of the spray equipment and increasing the cost of performing the job.
Another consideration is that the needle assembly typically includes a very fine-pointed needle that serves as a fluid valve and which operates to provide a finely-metered flow of liquid material through the nozzle. During disassembly and handling of the plurality of components of the prior art spray apparatus, there is an increased risk of dropping or otherwise mishandling the fine-pointed needle that may result in damage, thereby adversely impacting the performance and operability of the spray assembly.